Drum shells as sub enclosures?

[basham]

Can anyone comment on the drawbacks on using a Maple 10ply drum shell as an enclosure for a sonotube type sub. The drum shell has a wall thickness of .270"

I realize that real wood will potentially "color the sound", but thought I could get around this by using something like Cascades VB-1S PRO damping spray on the internal walls.

Any comments will be greatly appreciated.

[needtubes]

I would think this would be the same (if not better) as using cardboard sonotube for an enclosure. Plus, you have the advantage of having an attractive wood outer finish.

[johninCR]

It should look and work great. You will need to brace the 2 parallel circular baffles very well with each other, so they don't act like drum heads.

[paulspencer]

My feeling is that sonosubs aren't as inert as they could be. Adire use a novel way in their Sadhara to improve on them by using two with bracing in between so that the air in between acts like a vent with a very large area.

[johninCR]

The strength of a circle for the pressure of a fluid can't be disputed. I have a big ported pcv sub and the walls are totally dead. I did have to go with 2" thick end caps to avoid the need for bracing and it's only 12" dia pipe.

[paulspencer]

Originally posted by johninCR
The strength of a circle for the pressure of a fluid can't be disputed. I have a big ported pcv sub and the walls are totally dead. I did have to go with 2" thick end caps to avoid the need for bracing and it's only 12" dia pipe.

You are right, there is no disputing the strength side of things. But I'm not sure this is the complete picture.

It has strength and stiffness, but lacks mass and thickness. I expect there will still be a fair amount of sound transmission.

I suspect that the advantages of sonotube being a cylinder, although correct, are often overstated.

The question I would ask is can you feel vibration of the enclosure? If the answer is yes then energy is being both absorbed and transmitted in and through the enclosure.

[johninCR]

Paul,

That's what I'm saying, it's dead. I did have to strap it down to prevent movement from the mechanical operation of the woofer because it is so light, then there's no vibration on the cylinder walls. The only other sub I've built that comes close in that department is a well braced cube with 3/4" ply with a 1" outer layer of an extremely dense and heavy hardwood.

With the long wavelengths of a sub, I'm not sure there is sound on the inside. I think it's just pressure changes, one of those does the refrigerator light turn off kind of things.

[David Gatti]

That's a really intersting idea Basham.
How about using something like this for starters.
I would paint the inside with epoxy/fibreglass, fit plywood baffles to the front and back and mount the driver on the back. How cool is that!

[johninCR]

The inside doesn't need anything for strength, so spend the time and effort bracing the 2 baffles, especially to each other.

[basham]

Hello all,
Thanks for the great comments.

"It has strength and stiffness, but lacks mass and thickness. I expect there will still be a fair amount of sound transmission."

Paul, this was my concern from the beggining. This is why I had intended to spray the interior with some type of damping material,
hoping to eleminate, or at least minimize, any sound transmission.

"The inside doesn't need anything for strength, so spend the time and effort bracing the 2 baffles, especially to each other."

John, what would be the reasoning in bracing the endcaps together, if they were at least 1.5' thick and attached securely to the walls?

Once again, thanks for your replys